Sky & Telescope - July 2022 - 27

tude 44 Ophiuchi and then east to 4.8-magnitude 51 Ophiuchi.
Follow that arc another 1.5° or so to put the globular in
your eyepiece. Herschel discovered NGC 6401 on May 21,
1784, the last object he recorded for the sweep of that night.
A field star also marks NGC 6544. An 11th-magnitude
sparkle lies in the halo about 1.5′ southwest of the core.
The periphery of the cluster is seemingly resolved, but it's
likely foreground field stars that give that false impression.
NGC 6544 appears rather bright and somewhat elongated in
the northwest-southeast direction, with an irregular outline.
It lies about 1° southeast of the center of the Lagoon Nebula
(M8). Another degree southeast of NGC 6544 is NGC 6553,
which is more open and so appears larger. An 11.8-magnitude
star sits 45″ northwest of the core. The globular has a pleasing
appearance: It's mostly unresolved yet with considerable
speckling. Herschel discovered both objects on May 22, 1784.
Observers who enjoy seeking out globular clusters will
find the starry realm of the summer Milky Way a satisfying
hunting ground. More than 60 globular clusters sparkle
Summertime Globulars
Object
NGC 6144
NGC 6284
NGC 6293
NGC 6316
NGC 6304
NGC 6287
NGC 6235
NGC 6355
NGC 6356
NGC 6342
NGC 6642
NGC 6522
NGC 6528
NGC 6624
NGC 6712
NGC 6440
NGC 6717
NGC 6723
NGC 6441
NGC 6401
NGC 6544
NGC 6553
Const.
Sco
Oph
Oph
Oph
Oph
Oph
Oph
Oph
Oph
Oph
Sgr
Sgr
Sgr
Sgr
Sct
Sgr
Sgr
Sgr
Sco
Oph
Sgr
Sgr
Mag(v)
9.0
8.9
8.3
8.1
8.3
9.3
8.9
8.6
8.2
9.5
8.9
9.9
9.6
7.6
8.1
9.3
8.4
6.8
7.2
7.4
7.5
8.3
within 20° of the galactic center. It's instructive to recognize,
however, that this is a two-dimensional perspective effect. In
three dimensions, these objects lie quite far apart. The most
distant object on our tour, NGC 6356, at a distance of around
50,000 light-years, is about six times farther than NGC 6544,
which is the nearest. Near or far, however, they're some of
the most spectacular objects in the night sky. There's hardly
a better use for a summer evening than to spend it collecting
these celestial jewels in your eyepiece.
¢ Contributing Editor TED FORTE enjoys observing the deep
sky from his home observatory in southeastern Arizona. Have
you detected the planetary nebula JaFu 2 in NGC 6441? If yes,
please email him at tedforte511@gmail.com.
FURTHER READING Several websites aggregate the histories
of these and other NGC objects. Among them are: https://is.gd/
steve_gottlieb_ngc; http://haroldcorwin.net/ngcic/; and https://
is.gd/wolfgang_steinicke_ngc.
B * Mag(v)
13.4
-
14.3
15.0
14.5
14.5
14.0
-
15.1
15.0
-
14.1
15.5
14.0
13.3
16.7
14.0
12.8
15.4
15.5
12.8
15.3
HB * Mag(v)
16.5
16.6
16.5
17.8
16.2
17.1
16.7
17.2
17.7
16.9
16.3
16.9
17.1
16.1
16.3
18.7
15.6
15.5
17.1
18.0
14.9
16.9
Size/Sep
7.4′
6.2′
8.2′
5.4′
8.0′
4.8′
5.0′
4.2′
10.0′
4.4′
5.8′
9.4′
5.0′
8.8′
9.8′
4.4′
5.4′
13.0′
9.6′
4.8′
9.2′
9.2′
Class
XI
IX
IV
III
VI
VII
X
-
II
IV
-
VI
V
VI
IX
V
VIII
VII
III
VIII
V
XI
RA
16h 27.2m
17h 04.5m
17h 10.2m
17h 16.6m
17h 14.5m
17h 05.2m
16h 53.4m
17h 24.0m
17h 23.6m
17h 21.2m
18h 31.9m
18h 03.6m
18h 04.8m
18h 23.7m
18h 53.1m
17h 48.9m
18h 55.1m
18h 59.6m
17h 50.2m
17h 38.6m
18h 07.3m
18h 09.3m
Dec.
-26° 01′
-24° 46′
-26° 35′
-28° 08′
-29° 28′
-22° 42′
-22° 11′
-26° 21′
-17° 49′
-19° 35′
-23° 29′
-30° 02′
-30° 03′
-30° 22′
-08° 42′
-20° 22′
-22° 42′
-36° 38′
-37° 03′
-23° 55′
-25° 00′
-25° 54′
Angular sizes, as well as B * Mag(v) and HB * Mag(v) values, are from recent catalogs. Visually, an object's size is often smaller than the cataloged value and varies
according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox 2000.0. B * Mag(v) is the estimated brightness
of the brightest stars - your telescope must reach this magnitude to partially resolve the cluster. HB * Mag(v) is the estimated magnitude of the horizontal
branch - if your telescope reaches this magnitude, you'll see a well-resolved cluster. Class refers to the Shapley-Sawyer scale.
sk yand tele scope .o r g * JULY 2022 27
https://is.gd/steve_gottlieb_ngc https://is.gd/wolfgang_steinicke_ngc https://is.gd/steve_gottlieb_ngc http://haroldcorwin.net/ngcic/ https://is.gd/wolfgang_steinicke_ngc http://www.skyandtelescope.com
Sky & Telescope - July 2022

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